Fluid compressor

ABSTRACT

A fluid compressor includes a housing; a compression chamber within the housing; a motor; a shaft that is rotated by the motor; and a piston assembly including at least two pistons directly connected to each other without any connecting rods. The piston assembly performs a reciprocating motion when acted on by the shaft such that the at least two pistons move within the compression chamber to compress a fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Application No. 62/445,218, filed Jan. 11, 2017. This application isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

This application relates to various improvements in structures for fluidcompressors.

Refrigerant compressors are utilized to compress a refrigerant for usein a refrigerant cycle.

In two known types of refrigerant compressors, significant drawbacksexist that reduce performance and increase cost. First, in conventionalreciprocating compressors, a pair of pistons are driven to reciprocatewithin compression chambers by a motor. Fluid enters through an entrypassage in each compression chamber and exits through a dischargepassage. These passages are generally in a same surface of thecompression chamber, in a surface opposite the face of the piston. Thisclose proximity between the entry and discharge passages allows heatfrom the discharge passage to travel to the suction entry passage,heating up the fluid entering the chamber. This causes the fluid toexpand, which reduces the amount of fluid entering the chamber for eachstroke of the piston. Thus, the capacity of the compressor is reduced,and performance is reduced.

Second, in conventional scroll compressors, there are many placesthroughout the travel path of the fluid that can leak, especially athigher pressures. Accordingly, scroll compressors cannot provide highpressure operation or compression ratios. For example, compressionratios of over 7:1 are very problematic for scroll compressors, likelyleading to leaks as well as higher friction levels within thecompression passages and reduced performance.

The present invention seeks to address these deficiencies.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a fluid compressor includesa housing; a compression chamber within the housing; a motor; a shaftthat is rotated by the motor; and a piston assembly including at leasttwo pistons directly connected to each other without any piston rods.The piston assembly performs a reciprocating motion when acted on by theshaft such that the at least two pistons move within the compressionchamber to compress a fluid.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a compressor in accordance with oneembodiment of the present invention;

FIG. 2 is a side and cross-sectional view of the shaft and pistonassembly shown in FIG. 1;

FIG. 3 is a top view of an embodiment with 4 pistons that simultaneouslyproceed through their compression cycles;

FIG. 4 is an embodiment of a piston assembly for a 4 piston fluidcompressor that does not simultaneously compress;

FIG. 5 is a cross-section through an assembly of a horizontal embodimentof the present invention;

FIG. 6 is a cross-section through a compression chamber of analternative embodiment of the present invention; and

FIG. 7 is a close up cross-sectional view of the connection between thestator laminates and the housing of one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A fluid compressor 20 is illustrated in FIG. 1 having a suction tube 22providing a suction refrigerant into a suction chamber 24. A motor 26 ismounted within a housing, and drives a rotary shaft 28. Rotary shaft 28causes a piston assembly 30 to reciprocate a pair of attached pistons 35through the connection of yoke 29 and an eccentric pin 31. Thus, thepistons 35 are directly connected to piston assembly 30. Conventionalcompressors may attach the pistons to connecting rods which requiresmore labor and maintenance. The present invention eliminates theseproblems.

Suction plenums 32 lead the refrigerant from suction chamber 24 throughinlet valves 33 and into compression chambers 36, defined by a crankcaseor housing 34. Discharge valve assemblies 38 are placed at an oppositeend of each compression chamber 36 from the inlet valves 33. Therefrigerant passes outwardly through the discharge valves 38 into adischarge chamber 40, and then through a discharge tube 42. Thisdramatic separation of the suction discharge gas flow from the intakegas flow results in less heat pickup in the intake suction stream. Thisresults in more dense gas into compression chamber, which allowscompressor 20 to provide more capacity out of a smaller mechanism.

Further, the separation of the discharge valve 38 from the inlet valve33 maximizes the discharge volumetric geometry, allowing reducedpressure drops and improved fluid flow. This can be accomplished whetherthe gas is brought in through a valve on a face of the piston or througha valve in the bore (a side of the compression chamber) that is exposedwhen the piston retreats during the suction stroke. For example, FIG. 6shows a compression chamber with an inlet valve 33 on a lower sidesurface of the compression chamber. When the piston 35 retreats for asuction stroke, the valve 33 is exposed to the compression chamber. Thisagain allows a maximizing of the distance between the intake anddischarge valves, maximizing the discharge volumetric geometry.

By maximizing the discharge volumetric geometry, the size of thedischarge valve can be made significantly larger. A larger dischargevalve doesn't need to open as much to allow the compressed fluid out ofthe compression chamber. This improves valve timing and reduces backflowinto compression chamber, further improving performance.

The disclosed configuration also eliminates the need for any dischargemufflers, internal high pressure exhaust tubes, mechanical mountingsprings or mounts, cylinder heads, and valve plates. The elimination ofall of these parts also reduces manufacturing costs and maintenance. Inparticular, the volume in housing 34 of the discharge chamber ofcompressor 20 becomes a discharge muffler chamber. This eliminates theneed for a separate part for a discharge muffler.

FIG. 2 also shows high pressure relief valve 85. This valve is designedto vent the high pressure from the discharge side if that pressureexceeds a critical value. This prevents catastrophic failure of thecompressor housing. FIG. 2 also shows seal point 90, onto which ano-ring (not shown) is mounted. This seal prevents high pressurecompressed fluid from leaking back into the intake side.

In comparison to a scroll compressor, the present invention includes farfewer possible leakage paths. Thus, the present invention can perform atmuch higher compression ratios than a scroll compressor, such as greaterthan a 10:1 compression ratio. Thus allows for usage in suchapplications as medium and low temperature refrigeration, high ambienttemperature air conditioning, and more severe heat pump conditions.

Compressor 20 also includes lower bearing 70 and upper bearing 80. Thesebearings allow for a smaller sized motor, which results in greaterefficiently and lower cost.

As shown in FIG. 1, motor 26 is in direct contact with the inner surfaceof housing 21. This allows heat generated by motor 26 to moreefficiently escape the compressor 20. For example, FIG. 7 shows a closeup of the contact between the motor laminate layers 52 and the housing21. (Although the housing has a circular cross-section, the housing isshown in this view as having straight sides due to the small scale.)Each stator laminate layer 52 has a thickness of approximately 0.020 in.Each stator laminate layer 52 may then line up with a corresponding heatdissipation fin 23 on an outer surface of housing 21 to promote heattransfer from the laminate layer 52, through housing 21, and outcorresponding fin 23. Fin 23 is shown with a triangular cross-section,but any shape or configuration suitable for heat dissipation ispossible. These modifications are within the scope of the invention asclaimed.

Moreover, this direct connection to the outer housing means that thecompressor can be deployed in varying configurations, such as standingup or on its side. FIG. 5 shows a horizontal configuration of thepresent invention. The only changes needed to place the compressorhorizontally is the feet need to be moved to support the compressor.Also, the compressor 20 is not completely horizontal, but atapproximately 5-10 degrees from horizontal to ensure oil 60 can continueto be drawn into the bottom of lower bearing 70.

Further, as shown in FIG. 1, the outer housing is cylindrical. Incontrast, conventional compressor housings have an oval horizontalcross-section. The cylindrical outer housing of the present inventionhas several advantages. First, the circular cross-section is stronger,and thus higher pressure operation is possible, allowing highercompression ratios and higher performance. Further, the cylindricalshape creates a smaller oil sump volume 60 that must be filled with oil.Reducing the amount of oil needed saves costs throughout the lifetime ofthe compressor. Additionally, oval cross-sections may vibrate duringoperation of the compressor. This creates added noise that is notgenerated by the circular cross-section.

FIG. 3 shows an alternative embodiment which include 4 pistons 135, eachof which proceed through the compression cycle simultaneously. Springs137 are located in the compression chambers at an outer end to push thepistons 135 back when cam 139 moves to remove the force on piston 135.Cam 139 rotates on shaft 128, which is turned by a motor as in the firstembodiment. Thus, the forces on the pistons that could cause vibrationsin fact cancel out to eliminate bearing load and perfectly balance themechanism. This reduces noise, vibration, and power usage. Further,either or both of the modifications may be used within the scope of theinvention as claimed. That is, 2 piston unsynchronized, 4 pistonunsynchronized, 2 piston synchronized, and 4 piston synchronized are allwithin the scope of the invention as claimed.

In this regard, FIG. 5 shows a piston assembly for a 4 pistonunsynchronized configuration. This piston assembly includes a connectionportion 30A that extends above the piston surfaces to allow for aperpendicular piston assembly to reciprocate below the portion 30A asthe shaft rotates. Thus, 4 pistons can run in an unsynchronized mannerto compress fluid.

A worker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

What is claimed is:
 1. A fluid compressor comprising: a housing; acompression chamber within the housing; a motor; a shaft that is rotatedby the motor; and a piston assembly including at least two pistonsdirectly connected to each other without any connecting rods, the pistonassembly performing a reciprocating motion when acted on by the shaftsuch that the at least two pistons move within the compression chamberto compress a fluid.
 2. The fluid compressor as set forth in claim 1,wherein the piston assembly includes 2 pistons.
 3. The fluid compressoras set forth in claim 1, wherein the piston assembly includes 4 pistons.4. The fluid compressor as set forth in claim 3, wherein each of the 4pistons moves through a compression cycle simultaneously.
 5. The fluidcompressor as set forth in claim 1, wherein the motor is fixed directlyto an inner surface of the outer housing.
 6. The fluid compressor as setforth in claim 1, wherein fluid enters the compression chamber through afirst surface of the compression chamber and exits the compressionchamber through a second surface of the compression chamber that is anopposite surface from the first surface.
 7. The fluid compressor as setforth in claim 6, wherein the first surface is a surface of the at leastone piston.
 8. The fluid compressor as set forth in claim 1, whereinfluid enters the compression chamber through a first surface of thecompression chamber and exits the compression chamber through a secondsurface of the compression chamber that different from the firstsurface.
 9. The fluid compressor as set forth in claim 8, wherein thefirst surface is a bottom surface of the compression chamber.
 10. Thefluid compressor as set forth in claim 1, further comprising: aplurality of heat dissipation fins on an outer surface of the housing.11. The fluid compressor as set forth in claim 10, wherein each of theplurality of heat dissipation fins corresponds to a layer of statorlaminate of the motor within the housing.
 12. The fluid compressor asset forth in claim 1, wherein a discharge volume muffles noise createdwithin the compressor.
 13. The fluid compressor as set forth in claim 1,further comprising: an oil sump within a lower bearing that supports theshaft.
 14. The fluid compressor as set forth in claim 13, wherein theoil sump has a slanted surface having an angle of approximately 25-35degrees with a horizontal.